1. Field of the Invention
The present invention relates to a device for enlarging a machine table of a machine tool including a table plate, in particular a rectangular table plate, which can be attached at an end face on a longitudinal side or a transverse side of the table plate by a retaining means.
2. Description of the Related Art
Devices for enlarging machine tables of machine tools are used to extend machine tables when especially long workpieces are to be machined. Examples of machines in which these devices are used are woodworking machines such as routing machines, circular saws or planing machines. In known machine table extension devices, an end face of a rectangular table plate has a suspension rail which can be coupled to a retaining means which is designed as a fastening rail. The retaining means is fixed at its two ends so as to bear against the machine table edge, whereas it is at a distance from the machine table edge over most of its length so that the suspension rail can be mounted. At the opposite end, the table plate is supported on the floor via a foot which is of telescopic design for vertical adjustment.
The object of the present invention is to provide a device for enlarging a machine table which is suitable in particular for vertically adjustable machine tables, for example in planing machines, without a supporting foot of the table plate having to be adjusted in the process for adaptation to the varying height of the machine table.
In the case of the device of the generic machine table, the object is achieved by a device including a retaining means that comprises a supporting strip which can be fixed to an edge of the machine table and bears against the machine table edge essentially over the entire length and from which two cap screws project. The device further includes a table plate having two suspension slots for the positive-locking engagement of the cap screws, the suspension slots being arranged on an underside of the table plate and which are open at the bottom.
An essential advantage of this device over the prior art is that the table plate according to the present invention is fastened to the machine table in an overhung manner like a cantilever, thereby obviating the requirement for a supporting foot, which would have to be adjusted during every change in height of the machine table. Since the entire length of the supporting strip bears against the machine table edge and is firmly connected thereto, the supporting strip provides very stable retention of the table plate. If the two suspension slots are put over the cap screws for this purpose, there is no risk whatsoever of deflection of the table plate, which is attached in a load-bearing manner.
The two cap screws may be arranged at a smaller distance from the top edge of the supporting strip than from the bottom edge so that the bending moment about the horizontal produced by the weight of the table plate increases the stability of the fastening of the table plate. This has a positive effect on the accuracy of the plane passing through from the machine table to the table plate.
The supporting strip may be fixed to the machine table edge by stud bolts. The supporting strip may optionally include adjustable regulating pins for supporting the supporting strip on the machine table edge. The adjustable regulating pins are preferably arranged proximate the two longitudinal ends of the supporting strip. Inaccuracies of the machine table edge facing the supporting strip can be compensated for by these regulating pins, so that the table plate is always oriented accurately on a horizontal plane.
Alternatively, the supporting strip may be designed as an integral part of the machine table, wherein the cap screws are inserted directly into the machine table edge.
The heads of the cap screws may have radially oriented holes for receiving a pin-shaped locking and releasing tool. The cap screws can be adjusted and tightened with the pin-shaped locking and releasing tool after the table plate has been suspended for anchoring the table plate in a fixed and rigid manner on the machine table. Furthermore, the cap screws are precisely adjustable so that the table plate can easily be removed and suspended again free of play to create a continuous plane with the machine table.
The table plate is preferably rectangular and has a continuous cavity parallel to and proximate the region of the two longitudinal edges of the table plate. The continuous cavity includes a longitudinal slot open to the outside for connecting screws to pass through. Two table plates parallel to one another may be connected to form a wider unit using connecting screws which pass through the longitudinal slots. It is also possible to fasten angle strips to the table plate via the connecting screws in the longitudinal slots for extending the width of the table plate.
The continuous cavity may be designed for accommodating rectangular flat nuts for engagement with the connecting screws.
Elongated holes may be made in the underside of the table plate which open into the cavity and providing access for a locking and releasing tool to pass through for actuating heads of the connecting screws which have radial oriented holes.
According to a preferred embodiment of the invention, the rectangular table plate is designed in mirror symmetry relative to a vertical plane along its longitudinal center axis. In this way, it is especially simple to connect a plurality of table plates to one another without having to pay attention to precise lateral positions in the process.
It is advisable to produce the table plate from a light-alloy continuous casting with a hollow lattice profile, as a result of which very high bending rigidity is achieved with low weight.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.